1. Field of the Invention
The invention relates to a magnetic data embedding apparatus to write magnetic data (or embedded data) into a magnetic disk. More particularly, the invention relates to such an apparatus, which includes a servo pattern for detecting a magnetic head position, an ID pattern for identifying a magnetic disk, and a program into a virgin or unwritten magnetic disk.
In more detail, a magnetic data embedding apparatus according the invention is used in connection with writing data into a magnetic disk to meet customer requirements and so produce a product magnetic disk. The magnetic data embedding apparatus is also called a disk servo writer. Such a magnetic data embedding apparatus includes a master disk and a plurality of magnetic disks all stacked together onto the shaft of a spindle motor. The apparatus writes the embedded data on the surfaces of each magnetic disk based on magnetic data that is read out of the master disk. The magnetic data is read out to all of the magnetic disks simultaneously through magnetic heads disposed in such a way that a respective plurality of the magnetic heads is arranged on each magnetic disk surface.
According to an aspect of the invention, a magnetic data embedding apparatus has a checking function, in which the checking is executed for the embedded data written on the magnetic disk with the magnetic data on the master disk, and correction is performed for errors if detected, simultaneously with the writing operation.
2. Description of the Related Art
FIG. 9 shows a schematic arrangement of areas of magnetic data that are embedded (or written) on a virgin magnetic disk 1. Servo pattern embedding areas PS2 are arranged radially with an equal spacing (or in a sector spacing) on both sides of the magnetic disk 1. Data areas DTA are provided for an ID patterns for disk identification or for programs that are written on a customer's request at a time of manufacturing the magnetic disk 1. The data areas DTA also are provided for data that are written by a user after production of the magnetic disk 1.
The servo pattern PS2 consists of information for sensing the actual position of the magnetic head over the magnetic disk 1 during apparatus operation. The information includes a clock pattern for generating a synchronous clock and coordinate information such as a track address and a sector address.
FIGS. 7A and 7B show an example of a structure of a conventional magnetic data embedding apparatus 101 for writing a servo pattern PS2 on a magnetic disk 1. This magnetic data embedding apparatus comprises a disk stack unit DSU consisting of a stack of M (nine in FIG. 7B) magnetic disks 1 and a clock pattern disk 2K stacked coaxially therebelow. The DSU is fixed to the shaft of a spindle motor SPM and rotated at a high speed.
On the clock pattern disk 2K, a clock pattern PC0 is written on the outermost circumference, for example as shown in FIG. 8, on a virgin magnetic disk 1 using this apparatus 101, before writing servo pattern PS2 on the magnetic disk 1. The servo pattern PS2 is written on the magnetic disk 1, synchronizing with the clock that is obtained by reading out the clock pattern PC0.
A clock head 3K writes and reads a clock pattern PC0 directly to and from the clock pattern disk 2K. A clock head positioner 11K holds and positions the clock head 3K at a fixed position of the outermost circumference of the clock pattern disk 2K in the example of FIG. 7. The symbol 9K represents a clock pattern generator that generates signals of the clock pattern PC0 to write on the clock pattern disk 2K.
Servo heads 3 corresponding to each medium surface of the M magnetic disks 1 and write servo patterns PS2 directly on the medium surfaces. A rotary positioner 11 holds and stacks the servo heads 3, and oscillates around the shaft 11a to move the servo head 3 to a desired radial position on the magnetic disk 1.
An encoder 18 is fixed coaxially with the rotary positioner 11 and detects an angular position thereof. A position detection section 19 obtains a radial position (an analogue value) of the servo head 3 on the magnetic disk from the angular position detected by the encoder 18.
Servo compensator 7 and power amplifier 8, together with the encoder 18 and the position detection section 19, constitute a feedback loop that controls positioning of the servo heads 3 through the rotary positioner 11 in the radial direction on the magnetic disk. That is, the feedback loop serves, for a desired track, to position the servo heads 3 relative to the center of the disk in the radial direction.
The servo compensator 7 receives and amplifies an error signal between a target head position ρs and a detected head position ρ of the servo head 3 and obtains the value of a servo compensation necessary to minimize the error. Here, the target head position ρs is an analogue value corresponding to a radius of the target track and the detected head position ? is the actual radial position of the servo head 3 that is output from the position detection section 19. The power amplifier 8 outputs electric current for driving the rotary positioner 11 according to the obtained servo compensation value, to move the servo heads 3.
The servo pattern generator 9 generates servo pattern PS2 while receiving the clock from the clock head 3K, and supplies the generated servo pattern PS2 to each of the servo heads 3 stacked on the rotary positioner 11.
Next, the operation of the apparatus of FIG. 7 as a whole will be described. First, the clock head 3K records clock pattern PC0 generated by the clock pattern generator 9K at a desired radial position (at the outermost circumference in the example of FIG. 8) on the clock pattern disk 2K.
The actual radial position ρ of the servo head 3 is detected by the encoder 18 that is coaxial with the rotary positioner 11, and the position detection section 19. The amount of error between the detected head position ρ and the target head position ρs is fed back through the servo compensator 7 and the power amplifier 8 to the rotary positioner 11 thereby to move the servo heads 3 to the target position ρs.
In this state, each of the servo heads 3 simultaneously writes servo patterns PS2 generated by the servo generator 9 on the corresponding surface of the magnetic disk 1. Such writing is synchronized with the clock that is read out of the clock pattern disk 2K through the clock head 3K. In addition to the servo pattern, ID data, programs, and other data are also written onto the data area DTA of the magnetic disk 1 by the servo heads 3 through the servo pattern generator 9, while synchronizing with the clock that is read out of the clock pattern disk 2K.
Japanese Unexamined Patent Application Publication No. H5-189895 discloses a magnetic disk device comprising first and second access mechanisms, one of which writes data and the other of which reads and checks the data. Japanese Unexamined Patent Application Publication No. H9-288873 discloses a magnetic disk device comprising two magnetic heads, both of which access one magnetic disk surface, one of the two being dedicated to a regeneration operation only.
Japanese Unexamined Patent Application Publication No. H10-172254 discloses a technique with which a servo pattern read out of a master surface of a medium is written on medium surfaces excepting the master surface in a magnetic disk device comprising a plurality of medium surfaces. Japanese Unexamined Patent Application Publication No. H8-235801 and Japanese Unexamined Patent Application Publication No. 2001-216750 discloses a technique, in which a magnetic disk device or a disk servo writer writes servo information on a plurality of magnetic disk surfaces at the same time.
The conventional magnetic embedding apparatus described above, which is usually called a disk servo writer, simultaneously writes servo patterns generated by the servo pattern generator on the stacked magnetic disks, while synchronizing with the clock pattern recorded in advance on a clock pattern disk. The time required for writing on the entire disk surface of all disks in one disk stack unit is equal to the time for one revolution of the disks times the number of tracks to be written in each disk.
With increases in track density on magnetic disks, the time required for the writing operation increases, resulting in lower throughput. Since the track pitch decreases, more accurate writing is needed, and it becomes important to check the written pattern. This checking time also increases like the writing time, thus further decreasing the throughput.
By increasing the rotational speed of disks, the time for writing and checking can be reduced, but such increases in speed increases mechanical vibration. The vibration makes it difficult to write accurate servo pattern. Thus, there is tradeoff between speed and vibration.
If the number of magnetic disks in a stack is increased, while the throughput is enhanced, the load on the spindle motor increases. This causes precision of rotation to deteriorate. Since the number of stacked magnetic heads must also increase, it becomes difficult to assure that a specified degree of accuracy is reached in attaching the magnetic heads.
A conventional apparatus for embedding magnetic data employs a rotary encoder for detecting the position of the magnetic head. As recording density increases, the required accuracy in detecting the position of the magnetic heads may exceed the resolution precision of the rotary encoder. Therefore, a means for providing higher accuracy in position detection is needed.